Scandium is regarded as a critical raw material for the material industry, and the beneficiation from various primary sources is gaining attention. The utilization and development of the super-large silicate scandium ore in the Chuxiong area of Yunnan Province is becoming increasingly urgent. Therefore, systematic characterization was performed on raw ore samples to identify scandium‑bearing mineral types and occurrence features. The results reveal that the valuable component in this ore is scandium with a grade of 87.8 〖×10〗^(-4) wt.%, and the main scandium bearing mineral are diopside, plagioclase, amphibole, etc. Direct leaching is impractical owing to the low scandium content and complex mineral composition of the raw ore. A combined beneficiation pre-enrichment process was employed for the utilization of this ore, including magnetic separation, and shaking table. The main purposes include increasing the grade of the concentrate and discarding a portion of the gangue. Under the optimized conditions of low-intensity magnetic separation at 0.40 T, shaking table for particles greater than 0.074 mm at a stroke of 14 mm and punching frequency of 340 times per minute, a stroke of 12 mm and punching frequency of 380 times per minute, the high-intensity magnetic separation at 1.40 T, a scandium concentrate was obtained with a grade of 122×10⁻⁴ wt.%, recovery of 57.94%, and yield of 41.70%, respectively. This approach provides a technical basis for an integrated beneficiation process to support the comprehensive development and utilization of this critical resource.
Zinc leaching from a complex zinc ore using a mixture of citric and oxalic acids was investigated through response surface methodology (RSM) with a modified central composite design (CCD). The effects of solid content (2.5–12.5% w/v), citric acid stock solution concentration (0.25–1.25 M), oxalic acid stock solution concentration (0.05–0.25 M), leaching time (15–120 min), and temperature (30–70°C) were evaluated. Based on the F-values of the linear terms, the apparent order of influence was oxalic acid stock concentration > temperature > leaching time > citric acid stock concentration > solid content. This ranking represents linear main effects rather than overall variable importance, as significant interactions were also identified. Oxalic acid exhibited a strong negative linear effect, indicating that increasing its concentration did not improve Zn recovery. The highest experimental Zn recovery (67.98%) was obtained at 10% (w/v) solids, 1.0 M citric acid, 0.10 M oxalic acid, 30 min, and 60°C. Numerical optimization predicted a maximum Zn recovery of 81.42% at 10% (w/v) solids, 1.0 M citric acid, 0.10 M oxalic acid, 90 min, and 60°C. Three independent validation experiments yielded an average Zn recovery of 78.77 ± 1.10% (n = 3), corresponding to a relative prediction error of 3.25%. These findings demonstrate the effectiveness of RSM-based optimization and suggest that increasing oxalic acid concentration in the mixed-acid system may reduce Zn recovery.
To address the prominent issues associated with traditional mechanically stirred reactors, such as the tendency of forming localized flow dead zones at the bottom of the vessel, poor bubble dispersion, and uneven gas phase distribution, this study employs numerical simulation methods to analyze the characteristics of the gas-liquid two-phase flow field within the reactor. The study focuses on investigating the influence of the structural parameters of the gas distributor on gas phase distribution, fluid flow conditions, and gas-liquid mass transfer performance. The results indicate that the orifice diameter of the gas distributor has a significant impact on the distribution of the gas phase. While maintaining low shear stress level and avoiding damage to the growth of microorganisms or microbial communities in the ore leachate, reducing the orifice diameter can effectively improve bubble breakup and dispersion, enhance the uniformity of bubble distribution within the vessel, alleviate the problem of bubble stagnation in dead zones, and thereby increase gas hold-up and the volumetric oxygen mass transfer coefficient. The research findings reveal the mechanisms by which key structural parameters of gas distributor influence flow field characteristics and mass transfer performance, providing important theoretical references for the structural optimization of multi-phase reactors in fields such as mineral processing and biometallurgy.
Historical silicomanganese sludge deposits represent a potential secondary source of manganese, although its recovery is complicated by the heterogeneous chemical and mineralogical characteristics of the material. This study investigated the chemical, mineralogical and particle size characteristics of silicomanganese sludge and comparatively evaluated physical and hydrometallurgical approaches for manganese recovery. Thirty-five samples collected from the investigated deposit were characterised, and a representative composite sample was used for particle size classification, magnetic separation, density separation and hydrometallurgical experiments. Manganese was distributed throughout the entire particle size range, with limited enrichment in the finer fractions. Magnetic and density separation provided only partial pre-concentration, with overall manganese recoveries of approximately 27.4% and 24.4%, respectively. Hydrometallurgical treatment was investigated using HCl-water and aqua regia-water leaching systems, followed by sequential alkaline precipitation with KOH. Fe- and Al-bearing species were removed at controlled pH before recovery of the manganese-rich precipitate at pH 9–10. Under the most favourable conditions, the recovered products contained approximately 99–100% MnO equivalent, as determined by XRF, while the principal residual impurities were generally below 0.1%. Both leaching systems produced highly purified manganese-rich products, while the HCl-water route achieved comparable results without the use of aqua regia. The results demonstrate that physical separation provides only limited manganese pre-concentration, whereas acid leaching followed by selective purification and precipitation represents a promising route for the recovery of high-purity manganese-rich products from historical silicomanganese sludge.
Clay minerals have attracted increasing attention as low-cost, abundant, and structurally tunable catalyst supports for hydrogen generation reactions. In particular, sodium borohydride (NaBH₄)- based hydrogen generation provides an important platform for evaluating how mineral-derived supports influence catalytic activity, stability, metal dispersion, and interfacial reaction behavior. Among various hydrogen production routes, NaBH₄ hydrolysis and related catalytic hydrogen release processes have gained attention within the broader framework of green hydrogen technologies. In this system, catalyst support design plays a critical role in determining surface accessibility, active-site distribution, charge-transfer behavior, and long-term catalytic performance. This review examines the structural, morphological, physicochemical, and electrochemical roles of clay minerals in clay-supported catalytic systems for hydrogen generation, with particular emphasis on NaBH₄-based systems. The structural classification of phyllosilicates including 1:1 vs. 2:1-layer types, is discussed in relation to their corresponding morphologies, such as plate-like kaolinite, tubular halloysite, and swelling montmorillonite. Particular attention is given to morphology- and surface-chemistry-dependent catalytic mechanisms in NaBH₄ hydrolysis, where surface accessibility, interlayer characteristics, cation exchange capacity, metal-support interactions, and interfacial charge-transfer processes influence hydrogen generation performance. A comparative analysis of reported clay-supported systems published between 2020 and 2025 reveals that while tubular and high-cation-exchange-capacity structures may enhance metal dispersion, reactant diffusion, and catalytic stability. However, catalytic performance is not governed by morphology alone. Instead, metal distribution, thermal treatment effects, surface activation, support conductivity, and structural evolution during catalyst preparation frequently dominate the observed activity trends. By integrating mineralogical structure with catalytic and electrochemical function, this work provides a mechanistic framework for evaluating clay-based systems and discusses their future potential in photocatalytic, UV-responsive, and electrochemically hydrogen generation platforms. The findings highlight that rational catalyst design should consider both intrinsic clay architecture and processing-induced transformations to advance sustainable, mineral-derived catalytic materials for next-generation green hydrogen technologies.
